Injection solution, for instance to obtain local anesthesia within surgery or veterinary medicine, is normally stored in a glass vial being permanently sealed with a thick latex membrane as a sterility cover. The vial generally contains injection solution for several doses. The injection solution is transferred to a syringe by means of a thick withdrawal needle which is fitted on to the inlet opening of the syringe which is often designed as a male Luer cone. Subsequently, the latex membrane is sterilized by means of ethanol or the like whereupon the membrane is penetrated by the withdrawal needle and air is introduced under pressure into the vial by means of the injection syringe. Finally the volume desired of the injection solution is drawn into the syringe, the withdrawal needle is removed and replaced by a thinner injection needle and the solution is injected into the patient.
Unit dose containers for injection solutions are known, but the known unit dose containers, ampoules, are however intended to be inserted directly into an injection syringe of a special kind. They are made of glass and comprise both a penetratable membrane and a plunger. They are expensive to produce and are only suited for small volumes of injection liquid.
Thermoplastic unit dose containers sealed by means of a non-resealable cap are also known. The unit dose containers are however less adapted for injection solutions the sterility of which must be preserved also after the transfer into the injection syringe.